The invention concerns a rapid acting valve for gaseous and liquid media which is maintained in the open position by the force of a spring and closes against the force of the spring in the case of a sudden difference in pressure in the line against the force of the spring. Known rapid acting valves of this type have swivelling flaps or valve disks located in the direction of the flow of the medium which are directly exposed to pressure impacts so that the closing element strikes the valve seat with a high velocity and may thus be damaged.